def f(s,n):
 r=n;d=set(s)
 for i in d:
  for j in d:
   t=i+j+j;a=''
   for k in s:
    if t and k==t[0]:t=t[1:]
    else:a+=k
   if all((i!=j,i!='0',not t)):r=max(r,f(a,n+int(i+j+j)))
 return r
print(f(input(),0))